Several types of highly accurate liquid dosing devices are known in the art. A first type, which is commonly used in laboratory applications, is devices with step motor driven pumps. Dosing devices of a second type comprise small electric pumps, the pumping action of which is a result of the motion of a magnetisable internal pumping member, such as a ferromagnetic piston, causing a well-defined amount of liquid to be dispensed. Dosing devices of the second type may be embodied as low-cost pump units integrated in distribution containers for liquids and disposable together with these containers. Each pump unit may be actuated by means of an electromagnet arranged in a (non-disposable) structure for holding the liquid container. Such a dosing device, which is specially adapted for dispensing viscous liquids is known from GB 2 103 296 A, wherein a pumping chamber is defined by a flexible or resilient cylindrical chamber wall and non-return inlet and outlet valves. Pumping is effected by serial deformation of the pumping chamber by downward motion of a magnetisable circular element arranged at the top of the pumping chamber. Further, WO 2007/56097 A2 discloses a cartridge with a concentrate pumping device to be received by a dispenser. The dispenser is equipped with an electromagnet with a wound coil for acting on a piston slidably arranged in a dispensing tube in the pumping device, whereby the concentrate is forced out of the pumping device. Both of these, like other known dosing devices, are powered by electric mains.
Dosing devices of this nature would probably find more widespread use if powering by a portable voltage source, such as batteries, were available. For instance, it would be possible to increase the lifetime of a foodstuff liquid to be dispensed by storing and operating the dispenser in a refrigerator.